A cylinder head is typically used in combination with a main body of an internal combustion engine, to close one end of the cylinders formed in the main body of the internal combustion engine. The cylinders, pistons reciprocating in the cylinders, and the cylinder head define a combustion chamber having a variable volume therebetween. A valve is arranged in the internal combustion engine, to provide one of a flow of air and a mixture of air and fuel into the combustion chamber. Typically a separate valve is arranged in the cylinder head to provide exhausting of exhaust gases from the combustion chamber.
In most internal combustion engines, poppet valves are used to control the inflow and outflow of gases into the combustion chamber. These poppet valves are typically activated by a camshaft, which is rotatably coupled by a drive element to a crankshaft of the internal combustion engine. The rotatable coupling of the crankshaft to the camshaft provides a constant ratio between the speed of rotation of the crankshaft and the speed of rotation of the camshaft. The activation of the individual valves is thus fixed to the rotation of the crankshaft. Sometimes no independent control of the valves is possible even if it is desired to achieve improved engine performance and/or emission characteristics.
The poppet valves are typically spring biased to a closed position thereof. To open the valve, the camshaft has to first overcome the bias of the springs, which leads to large energy expenditure for opening of the valves.
An alternative cylinder head using spherical rotary intake and outlet valves accommodated therein is shown in U.S. Pat. No. 6,779,504, issued to Coates on Aug. 24, 2004. The Coates cylinder head is formed by two separate body portions. The body portions when assembled to each other define a plurality of spherical valve chambers. The valve chambers are each conformed to the shape of a single spherical valve to be accommodated therein. Each of the two body portions of the cylinder head has a plurality of cavities formed therein, which forms one half of the spherical valve chambers.
Separate cooling fluid chambers are provided within each of the separate body parts of the cylinder head. An upper one of the body parts has inlet passages connecting a respective valve chamber to an air manifold formed therein. A lower one of the body parts has inlet passages formed therein, connecting a respective valve chamber to an exhaust manifold.
Flow of air between the cylinder head and the cylinder is controlled by each of the spherical rotary valves accommodated in the cylinder head. In particular, flow of gases is allowed through an opening in the spherical surface of the rotary valve, which is brought into alignment with a flow opening in the lower body part of the cylinder head, and through the side surfaces of the spherical rotary valves. To provide a required air flow through the rotary valve, the rotary valve has to be of a certain size, and especially a certain height.
Especially if large air flows are required, the size of the rotary valve may become very large, thus necessitating a correspondingly large cylinder head to be used for accommodating the rotary valves. Such a large cylinder head leads to increased costs thereof. Furthermore, the body parts have to be separately manufactured, necessitating different molds for the respective bodies leading to high manufacturing costs for the body parts of the cylinder head. The surfaces of the body parts facing each other have to be machined, to allow sealing of the valve chambers formed thereby. Due to uneven heating of the separate body parts, the geometry of the valve chambers might changing during operation to thereby negatively affect the flow of fluid therethrough. The respective sizes of the inlet passages and the exhaust passages are partially limited by the height of the respective body part, in which they are formed, thereby affecting the maximum air flow through the cylinder head.
The present application is directed to overcoming one or more of the problems set forth above.